Randomized controlled trials (RCTs) of mutual aid are extremely difficult to conduct. The existing, mainly correlational, studies of Alcoholics Anonymous (AA) effectiveness are susceptible to two main kinds of artifacts due to potential endogeneity bias in variables, defined as when variables treated as exogenous may actually be endogenous. That is, they have presumed omitted causes that need to be explicitly represented in a causal model;this is also termed specification error. One such artifact is self-selection bias, i.e., where different types of people choose to participate or not participate in AA. An example of this would be a spurious relation between AA participation and drinking due to the possibility that individuals who develop motivation to stop drinking are more likely both to attend AA and to stop drinking;that is, high motivation could well "explain" the observed correlation between AA participation and drinking behavior. The second possible type of artifact is reverse causation, i.e., when reducing or stopping drinking leads to increased AA participation. It is essential to determine the true magnitude of effect and causal direction in the relation between AA participation and drinking behavior by controlling for these possible endogeneity biases, The overall objective of the study is to conduct a secondary analysis of AA participation and drinking behavior in the Project MATCH alcoholism treatment database using three statistical techniques which are designed to control for potential endogeneity biases in correlational data: propensity score matching (PSM), instrumental variable (IV) analysis, and structural equation modeling (SEM) of panel data with cross-lagged effects. Simulation modeling will also be conducted to test the robustness of the analyses with respect to violation of assumptions. The results could greatly strengthen the evidence base for Alcoholics Anonymous and 12 step facilitation therapy, as well as provide the recovery community with additional evidence useful for encouraging consumers to stay involved in mutual aid. PUBLIC HEALTH RELEVANCE: The results of this study could increase the utilization of 12 step facilitation therapies and 12 step mutual aid programs such as Alcoholics Anonymous to reduce public health and social problems attributable to excessive and hazardous alcohol consumption.